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HD 90156
HD 90156 is a star with an orbiting exoplanet in the constellation Hydra. Based on parallax measurements, it is located at a distance of 71.6 light years from the Sun. The system is drifting further away with a heliocentric radial velocity of 27 km/s. The apparent visual magnitude of this star is 6.92, which is places it near the lower limit of visibility to the naked eye. A survey in 2015 ruled out the existence of any stellar companions at projected distances above . This star was designated as Gamma Antliae by Lacaille, and Gould intended to keep it in the Antlia constellation. However, the delineating of constellation boundaries in 1930 saw it transferred to Hydra. The spectrum of HD 90156 presents as a G-type main-sequence star with a stellar classification of G5 V It is rotating slowly with a projected rotational velocity of 0.817, and it only displays a low level of magnetic activity in its chromosphere. The metallicity of the star is lower than in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydra (constellation)
Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees, and also the longest at over 100 degrees. Its southern end borders Libra (constellation), Libra and Centaurus (constellation), Centaurus and its northern end borders Cancer (constellation), Cancer. It was included among the 48 constellations listed by the 2nd century astronomer Ptolemy. Commonly represented as a water snake (other), water snake, it straddles the celestial equator. History and mythology Western mythology The Greek constellation of Hydra is an adaptation of a Babylonian astronomy, Babylonian constellation: the MUL.APIN includes a "serpent" constellation (MUL.DINGIR.MUŠ) that loosely corresponds to Hydra. It is one of two Babylonian "serpent" constellations (the other being the origin of the Greek Serpens), a mythological hybrid of serpent, lion and bird. The shape of Hydra resembles a twisting snake, and features as such in some Greek myths. One myth associates it w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallicity
In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matter in the universe is either hydrogen or helium, and astronomers use the word ''metals'' as convenient shorthand for ''all elements except hydrogen and helium''. This word-use is distinct from the conventional chemical or physical definition of a metal as an electrically conducting element. Stars and nebulae with relatively high abundances of heavier elements are called ''metal-rich'' when discussing metallicity, even though many of those elements are called ''Nonmetal (chemistry), nonmetals'' in chemistry. Metals in early spectroscopy In 1802, William Hyde WollastonMelvyn C. UsselmanWilliam Hyde WollastonEncyclopædia Britannica, retrieved 31 March 2013 noted the appearance of a number of dark features in the solar spectrum. In 1814, Jo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gliese And GJ Objects
Gliese may refer to: * Rochus Gliese (1891—1978), a German actor, director, production designer, and art director * Wilhelm Gliese (1915–1993), a German astronomer, best known for the Gliese Catalogue of Nearby Stars * Gliese Catalogue of Nearby Stars, a modern star catalog of stars located within 25 parsecs of the Earth ** Any of the stars in this catalog; see :Gliese and GJ objects {{Disambiguation, surname ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Durchmusterung Objects
In astronomy, Durchmusterung or Bonner Durchmusterung (BD) is an astrometric star catalogue of the whole sky, published by the Bonn Observatory in Germany from 1859 to 1863, with an extension published in Bonn in 1886. The name comes from ('run-through examination'), a German word used for a systematic survey of objects or data. The term has sometimes been used for other astronomical surveys, including not only stars, but also the search for other celestial objects. Special tasks include celestial scanning in electromagnetic spectrum, electromagnetic wavelengths shorter or longer than visible light waves. Original catalog The Bonner Durchmusterung (abbreviated BD), was initiated by Friedrich Wilhelm Argelander, Friedrich Argelander and using observations largely carried out by his assistants, which resulted in a catalogue of the positions and apparent magnitudes of 342,198 stars down to approximate apparent magnitude 9.5 and covering the sky from 90°N to 2°S declination. The cat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planetary Systems With One Confirmed Planet
Planetary means relating to a planet or planets. It can also refer to: Science * Planetary habitability, the measure of an astronomical body's potential to develop and sustain life * Planetary nebula, an astronomical object People * Planetary (rapper), one half of east coast rap group OuterSpace Arts, entertainment, and media * ''Planetary'' (comics), a comic book series by Warren Ellis and John Cassaday * "Planetary (Go!)", a 2011 song by rock band My Chemical Romance * ''Planetary Radio'', a public radio show about space exploration, produced by The Planetary Society Organizations * The Planetary Society, the Earth's largest space interest group Technology * Epicyclic gearing An epicyclic gear train (also known as a planetary gearset) is a gear reduction assembly consisting of two gears mounted so that the center of one gear (the "planet") revolves around the center of the other (the "sun"). A carrier connects the ... (planetary gearing), an automotive transmission te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G-type Main-sequence Stars
A G-type main-sequence star (spectral type: G-V), also often, and imprecisely, called a yellow dwarf, or G star, is a main sequence, main-sequence star (luminosity class V) of stellar classification, spectral type G. Such a star has about 0.9 to 1.1 solar masses and an effective temperature between about . Like other main-sequence stars, a G-type main-sequence star converts the Chemical element, element hydrogen to helium in its core by means of nuclear fusion. The Sun, the star in the center of the Solar System to which the Earth is gravitationally bound, is an example of a G-type main-sequence star (G2V type). Each second, the Sun fuses approximately 600 million tons of hydrogen into helium in a process known as the proton–proton chain (4 hydrogens form 1 helium), Mass–energy equivalence, converting about 4 million tons of matter to energy. Besides the Sun, other well-known examples of G-type main-sequence stars include Alpha Centauri, Tau Ceti, and 51 Pegasi. Description Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virginia
Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States, Atlantic Coast and the Appalachian Mountains. The state's List of capitals in the United States, capital is Richmond, Virginia, Richmond and its most populous city is Virginia Beach, Virginia, Virginia Beach. Its most populous subdivision is Fairfax County, Virginia, Fairfax County, part of Northern Virginia, where slightly over a third of Virginia's population of more than 8.8million live. Eastern Virginia is part of the Atlantic Plain, and the Middle Peninsula forms the mouth of the Chesapeake Bay. Central Virginia lies predominantly in the Piedmont (United States), Piedmont, the foothill region of the Blue Ridge Mountains, which cross the western and southwestern parts of the state. The fertile Shenandoah Valley fosters the state's mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Extrasolar Planets
A list is a set of discrete items of information collected and set forth in some format for utility, entertainment, or other purposes. A list may be memorialized in any number of ways, including existing only in the mind of the list-maker, but lists are frequently written down on paper, or maintained electronically. Lists are "most frequently a tool", and "one does not ''read'' but only ''uses'' a list: one looks up the relevant information in it, but usually does not need to deal with it as a whole".Lucie Doležalová,The Potential and Limitations of Studying Lists, in Lucie Doležalová, ed., ''The Charm of a List: From the Sumerians to Computerised Data Processing'' (2009). Purpose It has been observed that, with a few exceptions, "the scholarship on lists remains fragmented". David Wallechinsky, a co-author of '' The Book of Lists'', described the attraction of lists as being "because we live in an era of overstimulation, especially in terms of information, and lists help us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Plane
The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) and of an orbiting celestial body at two different times/points of its orbit. The orbital plane is defined in relation to a reference plane by two parameters: inclination (''i'') and longitude of the ascending node (Ω). By definition, the reference plane for the Solar System is usually considered to be Earth's orbital plane, which defines the ecliptic, the circular path on the celestial sphere that the Sun appears to follow over the course of a year. In other cases, for instance a moon or artificial satellite orbiting another planet, it is convenient to define the inclination of the object's orbit as the angle between its orbital plane and the planet's equatorial plane. The coordinate system defined that uses the orbital plane as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doppler Spectroscopy
Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star. As of June 2025, over 1,100 known extrasolar planets (about 19.0% of the total) have been discovered using Doppler spectroscopy. History Otto Struve proposed in 1952 the use of powerful spectrographs to detect distant planets. He described how a very large planet, as large as Jupiter, for example, would cause its parent star to wobble slightly as the two objects orbit around their center of mass. He predicted that the small Doppler shifts to the light emitted by the star, caused by its continuously varying radial velocity, would be detectable by the most sensitive spectrographs as tiny redshifts and blueshifts in the star's emission. However, the technology of the time produced radial-veloc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Eccentricity
In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit (or capture orbit), and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the Galaxy. Definition In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit. The eccentricity of this Kepler orbit is a non-negative number that defines its shape. The eccentricity may take the following values: * Circular orbit: * Elliptic orbit: * Parabolic trajectory: * Hyperbolic trajectory: The eccentricity is given by e = \sqrt where ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature when the body's emissivity curve (as a function of wavelength) is not known. When the star's or planet's net emissivity in the relevant wavelength band is less than unity (less than that of a black body), the actual temperature of the body will be higher than the effective temperature. The net emissivity may be low due to surface or atmospheric properties, such as the greenhouse effect. Star The effective temperature of a star is the temperature of a black body with the same luminosity per ''surface area'' () as the star and is defined according to the Stefan–Boltzmann law . Notice that the total ( bolometric) luminosity of a star is then , where is the stellar radius. The definition of the stellar radius is obviously not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
